Hybrid transformer for dc/dc converter

ABSTRACT

In at least one embodiment, a transformer assembly is provided. The assembly includes a first printed circuit board (PCB), a magnetic core, a primary winding, and a secondary winding. The magnetic core is positioned about the first PCB. The primary winding is implemented as a wire assembly and is positioned on a first side of the PCB to interface with the magnetic core. The secondary winding is embedded within the first PCB to interface with the primary winding and the magnetic core to convert an input signal into a converted output signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application Ser.No. 62/802,780, filed Feb. 8, 2019, the disclosure of which is herebyincorporated in its entirety by reference herein.

TECHNICAL FIELD

Aspects disclosed herein may generally relate to a transformer includingprimary and secondary windings in which one of the windings isimplemented as wiring and the other one of the windings is implementedas one or more metallic foils.

BACKGROUND

U.S. Publication No. 2008/0297300 to Ackerman et al. provides primaryand secondary windings that are subjected to a significant heat stressduring operation of a high voltage transformer. Ackerman furtherdiscloses that a high voltage transformer is believed to have goodtemperature properties. This transformer may have a planar primarywinding and a Litz secondary winding. The planar primary winding mayabut against a planar face of the core thereby allowing for a good heatexchange between these two elements. The Litz secondary winding and theplanar primary winding may be cooled by means of a cooling medium.

SUMMARY

In at least one embodiment, a transformer assembly is provided. Theassembly includes a first printed circuit board (PCB), a magnetic core,a primary winding, and a secondary winding. The magnetic core ispositioned about the first PCB. The primary winding is implemented as awire assembly and is positioned on a first side of the PCB to interfacewith the magnetic core. The secondary winding is embedded within thefirst PCB to interface with the primary winding and the magnetic core toconvert an input signal into a converted output signal.

In at least another embodiment, a power conversion device including atransformer assembly is provided. The transformer assembly receives aninput signal. The assembly includes a first printed circuit board (PCB),a magnetic core, a primary winding, and a secondary winding. Themagnetic core is positioned about the first PCB. The primary winding isimplemented as a wire assembly and being positioned on a first side ofthe PCB to interface with the magnetic core. The secondary winding isembedded within the first PCB to interface with the primary winding andthe magnetic core to convert the input signal into a converted outputsignal.

In at least one embodiment, a transformer assembly is provided. Theassembly includes a first printed circuit board (PCB), a magnetic core,a primary winding, and a secondary winding. The magnetic core ispositioned about the first PCB. The primary winding is implemented as aLitz wire and is positioned on a first side of the PCB to interface withthe magnetic core. The secondary winding is embedded within the firstPCB to interface with the primary winding and the magnetic core toconvert an input signal into a converted output signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the present disclosure are pointed out withparticularity in the appended claims. However, other features of thevarious embodiments will become more apparent and will be bestunderstood by referring to the following detailed description inconjunction with the accompany drawings in which:

FIG. 1 depicts an example of a perspective view for a transformerimplementation (or transformer assembly) in accordance to oneembodiment;

FIGS. 2A-2B generally depict one example of a printed circuit board(PCB) and at least a portion of a magnetic core that forms a portion ofthe transformer assembly of FIG. 1;

FIGS. 3A-3B generally depict one example of a primary winding that formsat least a portion of the transformer assembly of FIG. 1;

FIG. 4 generally depicts another example of transformer assemblyincluding a plurality of transformers in accordance to one embodiment;

FIG. 5 generally depicts a top view of the PCB in accordance to oneembodiment

FIG. 6 generally depicts an underside of the PCB that forms thetransformer assembly in accordance to one embodiment'

FIG. 7 generally depicts a more detailed example of another transformerassembly in accordance to one embodiment;

FIG. 8 depicts a perspective view for another transformer assembly inaccordance to one embodiment;

FIG. 9 depicts a perspective view of another transformer assembly inaccordance to one embodiment;

FIG. 10 depicts a table of partitions of a secondary winding as embeddedin various layers of the PCB in accordance to one embodiment; and

FIG. 11A-11D generally depict a top view for a corresponding a layer ofthe PCB with sectors and segments of the secondary winding.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

It is recognized that directional terms that may be noted herein (e.g.,“upper”, “lower”, “inner”, “outer”, “top”, “bottom”, etc.) simply referto the orientation of various components of a busbar assembly asillustrated in the accompanying figures. Such terms are provided forcontext and understanding of the embodiments disclosed herein.

A power conversion device such as, for example, a direct current (DC) toDC converter (hereafter “DC/DC converter) converts a DC input voltagefrom one value into a DC output voltage that differs from the DC inputvoltage. More particularly, a boost DC/DC converter converts a DC inputvoltage with a DC input current into a higher DC output voltage with alower DC output current. Conversely, a buck DC/DC converter converts aDC input voltage with a DC input current into a lower DC output voltagewith a higher DC output current.

A DC/DC converter includes, but not limited to, a set of input powerswitches, a transformer, and a set of output power switches. The inputpower switches are controlled to invert the DC input voltage into an ACinput voltage. The transformer transforms the AC input voltage into anAC output voltage having a different voltage level. The output powerswitches are controlled to rectify the AC output voltage into the DCoutput voltage.

As examples, DC/DC converters may be configured to provide the followingDC input/output pairings: 400-12; 48-12; 400-48; and 400-800. As such,for instance, a 400-12 V DC/DC converter may be used to convert a 400 VDC input into a 12 V DC output. Additionally or alternatively, the400-12 V DC/DC converter may be used between a 400 V DC network and a 12V DC network to thereby connect these two voltage networks together. Ofcourse, the DC/DC converters are usable over voltage ranges. Forinstance, the 400-12 V DC/DC converter may be used to convert a DC inputvoltage falling within a voltage range of 250-470 V DC into a DC outputvoltage into a 12 V DC output voltage.

A vehicle may have a high-voltage (HV) network and a low-voltage (LV)network. In this case, a DC/DC converter may be used to connect the HVand LV networks together. Consequently, a high DC input voltage of theHV network may be converted by the DC/DC converter into a low DC outputvoltage for use by loads connected to the LV network. Conversely,assuming the DC/DC converter is bidirectional, a low DC input voltage ofthe LV network may be converted by the DC/DC converter into a high DCoutput voltage for use by loads connected to the HV network.

In a DC/DC converter implemented as a packaged electronic componentassembly, the power switches and the transformer are mounted on aprinted circuit board (PCB). The transformer includes but not limitedto, a primary winding, a secondary winding, and a magnetic core. Theprimary winding may be wrapped around a portion of the magnetic core andthe secondary winding may be wrapped around another part of the magneticcore. In one example, both windings may be implemented as respectivewirings. In specific cases, both windings may be fully embedded in thePCB.

For reference, a transformer in which both windings are fully embeddedin the PCB may not be preferable for creepage or insulation distances.As a component, high electrical currents in the secondary winding mayrequire large physical connections to the associated power switches aswell as potting with thermal paste for heat dissipation. Aspectsdisclosed herein may mitigate creepage or isolation distances and aswell as eliminate the need for large physical components (orconnections).

As noted above, current vehicle architectures may need DC/DC powerconversion to support energy equalization across the different powerdomains. Several converter architectures may be possible for therespective applications (e.g. 48V/12V DC/DC (bidirectional), 400V/12VDC/DC (unidirectional), 400V/48V DC/DC (unidirectional orbidirectional), 800V/12V DC/DC, etc.). In the low and mid voltagedomain, a key factor may be the magnetic integration. It has beenexperimentally tested that for low and mid voltage power conversion, ahybrid magnetic integration can introduce several benefits in terms ofefficiency increase and thermal management. Magnetics for powerapplications and low voltage may include a bulky integration ofconductor wires due to the handling of large electrical currents.

The embodiments as set forth herein may, but not limited to, provide amagnetic assembly that integrated in into a printed circuit board (PCB)on the low/medium voltage domains, while a wound up (or winding)approach may be used for the high voltage area. Such a concept mayremove high electrical current interconnections. This approach may alsoimprove power density, thermal management, and design efficiency.

FIG. 1 depicts an example of a perspective view for a transformerimplementation (or transformer assembly) 100 in accordance to oneembodiment. In one example, the transformer assembly 100 may be used inconnection with a 2 KW hybrid transformer implementation for HV-LV DC/DCconverter applications. As shown, the transformer assembly 100 includesa printed circuit board (PCB) 102, a primary winding 104, and a magneticcore 106. A plurality of electronics 108 may be positioned on the PCB102 to enable signal conversion. Such electronics 108 may include anynumber of controllers (microprocessors), switches (e.g. field effecttransistors (FETS), metal oxide semiconductor field effect transistors(MOSFETs), etc.), capacitors, inductors, etc. to enable voltageconversion between two different voltage domains.

A secondary winding 210 (see FIGS. 2A-2B) may be positioned below theprimary winding 104. The magnetic core 106 generally surrounds to theprimary winding 104 and the secondary winding 210. The primary winding104, the magnetic core 106, and the secondary winding 210 form a singletransformer 101. The secondary winding 210 may be embedded into variouslayers of the PCB 102 as a magnetic foil. This aspect will be discussedin more detail below. The primary winding 104 may be implemented as awire assembly, for example, as a Litz wire. As shown, the primarywinding 104 may be positioned on a top surface of the PCB 102.Additionally, the primary winding 104 may also be positioned above thesecondary winding which is embedded into the layers of the PCB 102. TheLitz wire of the primary winding 104 may be wound together to form anopening 110 thereof. A first extending portion 112 of the magnetic core106 may extend into the opening 110.

FIGS. 2A-2B generally depict one example of the PCB 102 and a lowerportion of the magnetic core 106 a that form a portion of thetransformer assembly 100 of FIG. 1. The magnetic core 106 may be formedof the lower (or first) portion 106 a and an upper (or second) portion106 b (not shown in FIGS. 2A-2B). While not shown, the lower portion 106a and the upper portion 106 b may be coupled together to form a singlemagnetic core 106. The lower portion 106 a and the upper portion 106 bmay be coupled together via adhesive or other suitable mechanism. Asshown, the lower portion 106 a may include a plurality of lowerextending portions 114 a-114 c. The PCB 102 includes a plurality ofopenings 116 a-116 c formed therein. The PCB 102 and the secondarywinding 210 define the opening 116 b. The plurality of lower extendingportions 114 a-114 c of the lower portion 106 a are may be inserted viaan underside of the PCB 102 into the plurality of openings 116 a-116 c,respectively (see FIG. 2A). The lower extending portion 114 b extendsthrough the PCB 102 and the secondary winding 210. The lower portion 106a of the magnetic core 106 generally includes a generally planar basemember 118 (or base member 118) from which the lower extending portions114 a-114 c extend therefrom. While the shape of the lower portion 106 amay generally be E-shaped, it is recognized that the overall shape andsize of the magnetic core 106 may change based on the particular desiredimplementation. The magnetic core 106 may be formed of a ferrite-basedmaterial.

FIGS. 3A-3B generally depict one example of the primary winding 104 thatforms at least a portion of the transformer assembly 100 of FIG. 1. Asnoted above, the primary winding 104 generally includes a wire (e.g.,Litz wire). The primary winding 104 also includes a spool 130 thatsupports the wire of the primary winding 104. The wire may be woundaround the spool 130 thereby forming layers of wires which increases theoverall size of the package. Specifically, the spool 130 may define anouter channel 133 that extends around an outer perimeter thereof forretaining the wire as the wire is wound around the spool 130 (see FIG.3B). A fastening mechanism 131 such as tape or adhesive may be coupledto the wires while in the wound position to keep the wires in place withrespect to the spool 130. The overall length of the wire may vary basedon the amount of inductance that may be needed for a particular desiredimplementation. The spool 130 defines an opening 132 for receiving thelower extending portion 114 b of the lower portion 106 a of the magneticcore 106 and the first extending portion 112 of the upper magnetic core106 b. FIG. 3B generally illustrates a back side of the primary winding104. As shown, the opening 132 extends from the front side of the spool130 through to the back side of the spool 130 (i.e., from the front sideof the primary winding 104 through to the back side of the secondarywinding 210). The spool 130 generally includes a first portion 133 ahaving a rounded portion thereof and a second portion 133 b also havinga rounded potion thereof. The first portion 133 a and the second portion133 b are generally positioned on opposite sides of the opening 132 andenable the Litz wire to be wrapped into fitted into the spool 130.

FIG. 4 generally depicts another example of transformer implementation(or transformer assembly) 300 including a plurality of transformers 101a and 101 b in accordance to one embodiment. Each of the transformers101 a and 101 b include the primary winding 104, the magnetic core 106(including the lower (or first) portion 106 a and the upper (or second)portion 106 b) and the secondary winding 210. Thus, the transformerassembly 300 includes the plurality of transformers 101 a and 101 b toprovide increased voltage/power capability. The lower portion 106 a andupper portion 106 b for each transformer 101 a,101 b may be coupledtogether via adhesive or other suitable mechanism.

A spring 302 may be attached to openings 303 that are positioned onsides of the lower portions 106 a of the magnetic cores 106, to attachthe magnetic cores 106 to the respective primary windings 104 and to thePCB 102. An attachment pad 304 (see also FIG. 6 for reference) may beprovided and positioned on an underside of the PCB 102 and may beintegrally formed with the lower portion 106 a of the magnetic core 106.In this case, the spring 302 when inserted into the openings 303 of thelower portions 106 a of the magnetic core 106 apply a downward forceagainst the upper portions 106 a of the magnetic core 106 to therebycause the attachment pad 304 to compress against the underside of thePCB 102. In response to the spring 302 acting on the upper portions 106a of the magnetic core 106 and the attachment pad 304 compressingagainst the underside of the PCB 102, the magnetic cores 106 compressinto the opening 132 and retain the primary windings 104 about the PCB102.

FIG. 5 generally illustrates that the PCB 102 is populated with thetransformer 101 a in addition to the primary winding 104, the magneticcore 106, and the secondary winding 210. While the PCB 102 may includethe transformer 101 b as shown in FIG. 4, FIG. 5 illustrates thesecondary winding 210 that may be used in connection with thetransformer 101 b. Each of the secondary windings 210 as illustrated inFIG. 5 may be embedded into the PCB 102.

FIG. 5 also depicts a footprint 500 defined by the PCB 102 for receivinga second primary winding 104 b in accordance to one embodiment. Thefootprint 500 of the PCB 102 generally includes the plurality ofopenings 116 a-116 c as noted in connection with FIG. 2A. The pluralityof lower extending portions 114 a-114 c of the lower portion 106 a ofthe magnetic core 107 may be inserted into an underside of the PCB 102into the plurality of openings 116 a-116 c, respectively (see referencenumbers 114 a-114 c of the lower portion 106 a as set forth in FIG. 2A).

FIG. 7 generally depicts a more detailed example of another transformerassembly 400 in accordance to one embodiment. The transformer assembly400 generally includes the plurality of transformers 101 a, 101 b toalso provide increased voltage/power capability. The transformerassembly 400 includes various electronics 402 that are positioned on thePCB 102 to perform DC/DC conversion. The transformer assembly 400 isgenerally similar to the assembly 100 with the exception of multipletransformers being utilized. Each of the transformers 101 a and 101 binclude the primary winding 104, the magnetic core 106 and the secondarywinding 210. While not shown in FIG. 7, each magnetic core 106 for eachtransformer 101 a and 101 b includes a corresponding lower (or first)portion 106 a and an upper (or second) portion 106 b. However, in theassembly 400, a fixation element 401 is provided that is positioned overthe magnetic cores 106 for the transformer 101 a, 101 b. The fixationelement 401 may be utilized to couple the magnetic cores 106 to theprimary coils 104 and to the PCB 102.

The fixation element 401 generally includes a plurality of openings 402a-402 n to receive attachment mechanisms 404 a-404 n. A correspondingattachment mechanism 404 a-404 n may be inserted into a respectiveopening 404 a-404 n to couple the fixation element 401 to the PCB 102.The PCB 102 may include a corresponding opening (not shown) that ispositioned below a corresponding opening 402 a, 402 b, 402 c, . . . ,402 n to also receive the respective attachment mechanism 404 a, 404 b,404 c, . . . 402 n. Likewise, the lower portions 106 a of the magneticcores 106 may include openings (now shown) to receive the attachmentmechanisms 404 a-404 n. The fixation element 401 applies a downwardforce against the magnetic cores 106 in response to the attachmentmechanisms 404 a-404 n being inserted into the openings 404 a-404 n. Thefirst extending portion 112 of the magnetic cores 106 may then beinserted into the openings 110 formed in the primary windings 104 alsoin response to the attachment mechanisms 404 a-404 n being inserted intothe openings 404 a-404 n. The fixation element 401 couples the magneticcores 106, the primary windings 104, the second windings 210 and the PCB102 to one another.

A cooling chamber (or housing) 450 may be positioned on an underside ofthe PCB 102. The cooling chamber 450 is generally configured to receivecoolant to cool various power elements (or switching devices) that maybe positioned on an underside of the PCB 102. In addition, the coolingchamber 450 may also receive the coolant to deliver to the lower portion106 a of the magnetic core 106 to cool the magnetic core 106. Thechamber 450 generally includes at least one inlet mechanism 452 and atleast one outlet mechanism 454. The coolant may be delivered to thecooling chamber 450 via the inlet mechanism 452 and passed from thecooling chamber 450 via the outlet mechanism 454. A gap (not shown) maybe defined between the underside of the PCB 102 and a top side (or topsurface) not shown of the cooling chamber 450. In this case, variouspower electronics that generate heat and the lower portion 106 a of themagnetic core 106 may be in contact with the top surface of the coolingchamber 450 to receive the coolant. In general, the coolant contacts thesurface of the housing 450 that contacts the heat generating devices onthe PCB 102 in addition to an underside of the magnetic core 106 to coolthe same. The coolant remains enclosed within the housing 450 and doesnot directly contact the heat generating device and the magnetic core.The fixation element 401 may also connect to top surface of the housing450 so that the screws or other attachment mechanisms fix the electroniccircuit assembly (transformer, PCB, etc.), while, at the same time,ensure proper contact of the bottom surface of magnetic core 106 withthe top surface of the housing 450.

FIG. 8 depicts an example of a perspective view for another transformerassembly 600 in accordance to one embodiment. The transformerimplementation 600 generally includes a first PCB 102 a, a second PCB102 b, the primary winding 104, the magnetic core 106 including thelower and upper portions 106 a, 106 b, and various electronics 402. Inthis case, the first PCB 102 a may be positioned on a top side of theprimary winding 104 and the second PCB 102 b may be positioned on abottom side of the primary winding 104. A first secondary winding 602 athat is implemented as a magnetic foil may be positioned directly abovethe primary winding 104 and is embedded into the first PCB 102 a. Theupper portion 602 a of the magnetic core 106 may be positioned directlyabove the secondary winding 104. A second secondary winding 602 b thatis implemented as a magnetic foil may be positioned directly below theprimary winding 104 and is embedded into the second PCB 102 b.

The transformer assembly 600 may be implemented as a DC/DC converterthat includes two secondaries (e.g., the first secondary winding 602 aand the second secondary winding 602 b). It is recognized that each ofthe first secondary winding 602 a and the second secondary winding 602 band their corresponding electronics may comprise two parallel circuitsthat may be generally equal to one another. Each secondary winding 602a, 602 b may handle half of the current for the DC/DC converter. Thisenables the electronics to be at rated at lower voltages which mayprovide a cost savings. While now shown, it is recognized that theprimary winding 104 generally provides an input to each of the firstsecondary winding 602 a and the secondary winding 602 b. Additionally,an output is provided between the first PCB 102 and the second PCB 102 bto electrically couple these PCBs 102 a, 102 b to one another.

With reference to FIGS. 2A and 8, each of the first PCB 102 a and thesecond PCB 102 b may include the plurality of openings 116 a-116 c forreceiving extending portions 114 a-114 c of the lower portion 106 a andthe upper portion 106 a of the magnetic core 106. For example, theextending portions 114 a-114 c from the upper portion 106 a of themagnetic core 106 may be inserted through a top side of the first PCB102 a into the plurality of openings 116 a-116 c, respectively.Similarly, the extending portions 114 a-114 c from the lower portion 106b of the magnetic core 106 may be inserted through a bottom side of thesecond PCB 102 b into the plurality of openings 116 a-116 c,respectively. With continuing reference to FIGS. 2A and 8, each of thelower portion 106 a and the upper portion 106 b of the magnetic core 106generally includes the base member 118 from which the extending portions114 a-114 c extend therefrom.

FIG. 9 depicts a perspective view of another transformer assembly 700 inaccordance to one embodiment. The transformer implementation 700generally includes the PCB 102, the primary winding 104, the magneticcore 106 including the upper portion 106 a and the lower portion 106 b.Similarly, as disclosed above, a secondary winding 702 may be embeddedinto the PCB 102. A heat sink 704 may be positioned adjacent to theupper portion 106 a of the magnetic core 106 and on a top surface of thePCB 102. Thermal paste 706 is provided between the heat sink 704 and thePCB 102 to attach the heat sink 704 to the PCB 102. A plurality of powerswitching devices 708 (e.g., MOSFETS) may be positioned on the PCB 102and contact the heat sink 704 and the thermal paste 704. In this case,heat generated by the power switching devices 708 may be transmitted tothe thermal paste 706 and to the heat sink 704 to draw heat away fromthe transformer apparatus 700. The transformer apparatus 700 may providefor a simpler manufacturing process, improved device performance (e.g.,improved layout: gating loops and power planes (Vbus)), and an improvedsecondary winding arrangement to ensure balanced current distribution.

FIG. 10 depicts a table 800 corresponding to partitions of the secondarywinding 210 as embedded in various layers 802 a-802 d of the PCB inaccordance to one embodiment. The table 800 illustrates the manner inwhich various current carrying sectors (i.e., sectors) are positioned onsegments of each layer of the PCB 102 and also illustrate the manner inwhich current flows through the layers 802 a-802 d. The PCB 102 maycomprise a total number of four layers (e.g., a top layer 802 a, a firstintermediate layer 802 b, a second intermediate layer 802 c, and a thirdintermediate layer 802 d). Each layer is generally positioned into foursegments (e.g., 1, 2, 3, 4) (see also FIGS. 11A-11D) which remainconstant from layer to layer (see FIGS. 11A-11D as segments 1, 2, 3, and4 are similarly designated and positioned in each of these FIGUREs). Perlayer 802 a, 802 b, 802 c, 802 d, there are corresponding sectors (orcurrent carrying conductors) 810 a, 810 b, 810 c, 810 d. In each layer802 a, 802 b, 802 c, 802 d; the various sectors 810 a, 810 b, 810 c, 810d conduct current horizontally in the PCB 102. This will be discussed inmore detail below. Table 800 illustrates the vertical positions of thesectors 810 a-810 d in reference to the segments 1-4 for each respectivelayer 802 a-802 d for vertical current flow or alternatively to adescription of split current flow per each sector 810 a-810 b.

Table 800 depicts that each sector 810 a-810 d is positioned on adifferent segment for each layer 802 a-802 d for the PCB 102. Thiscondition may mitigate or minimize the parasitic currents between thecorresponding layers 802 a-802 d since no two vertically adjacentsectors (or segments) are similar to one another. Alternatively, sinceno two vertically-adjacent sectors in a given segment of the PCB 102 areadjacent in the next segment. By implementing the metallic foil of thesecondary winding 800 into the layers 802 a-802 d of the PCB 102 andinto different segments 1-4 for each sector 810 a- 810 d for each layer802 a-802 d, this configuration may ensure that current flows not onlyon the top or bottom layers 802 a and 802 d, respectively, of the PCB102; but also through the first intermediate layer 802 b and the secondintermediate layer 802 c to maximize current flow over a larger crosssectional area of the PCB 102.

FIGS. 11A-11D generally depicts a top view for a corresponding a layer802 a-802 d of the PCB 102 with sectors 810 a-810 d and segments 1-4 ofthe secondary winding 210 in accordance to one embodiment. Current alsoflows horizontally through each segment 1, 2, 3, 4 in a correspondinglayer 802 a-802 d. For example, FIGS. 11A-11D illustrate a correspondingcurrent flow 900 starting at segment 1 and on to segment 4 for eachlayer 810 a-810 d. Conductive vias 902 are provided to enable current toflow from one segment to another segment (or of the same sector but in adifferent PCB layer) from one PCB layer to another PCB layer. Likewise,the vias 902 enable current to vertically flow to the different layers802 a-802 d.

The vertical flow of current that flows through the various sectors 810a-810 d of the layers 802 a-802 d will be explained as follows (see FIG.10). In reference to sector 810 a, current flows from segment 1 in layer802 a down to segment 2 in layer 802 b, down to segment 3 in layer 802 dand up to segment 4 in layer 802 c.

In reference to sector 810 b, current flows from segment 1 in layer 802c, up to segment 2 in layer 802 a, down to segment 3 in layer 802 b,down to segment 4 in layer 802 d (see FIG. 10). In reference to sector810 c, current flows from segment 1 in layer 802 d, up to segment 2 inlayer 802 c, up to segment 3 in layer 802 a, down to segment 4 in layer802 b (see FIG. 10). In reference to sector 810 d, current flows fromsegment 1 in layer 802 b, down to segment 2 in layer 802 d, up tosegment 3 in layer 802 c, up to segment 4 in layer 802 a (see FIG. 10).

In general, for horizontal current flow, each segment conducts thecurrent horizontally in a counter-clockwise direction. Then at eachsegment end there is a via-array connection to provide a verticaltransfer of current to the following segment (in number) but in anotherPCB layer (as indicated in the table 800). Thus, current may primarilyflow horizontally.

The segments are designated such that each sector starts in a segment 1,then connects to a segment 2, then to a segment 3 and finally ends in asegment 4. But for each sector, the order of layers used for eachsegment is generally different. All segments “1s” in the differentlayers 802 a-802 d are interconnected and all segments “4s” in thedifferent layer 804 a-804 b are interconnected transfer the current tothe respective sets of electronic devices (e.g., switches and so on).FIGS. 11A-11D illustrate that each given sector 810 a-810 d ispositioned on a different segment for each layer 802 a-802 d and thiscondition may mitigate parasitic currents within the PCB 102.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. A transformer assembly comprising: a firstprinted circuit board (PCB); a magnetic core positioned about the firstPCB; a primary winding implemented as a wire assembly and beingpositioned on a first side of the PCB to interface with the magneticcore; and a secondary winding embedded within the first PCB to interfacewith the primary winding and the magnetic core to convert an inputsignal into a converted output signal.
 2. The transformer assembly ofclaim 1, wherein the magnetic core includes a first extending portionthat extends through a first opening of the first PCB and the secondarywinding and is received in an opening formed in the primary winding. 3.The transformer assembly of claim 2, wherein magnetic core includes aplanar base member from which the first extending portion extendsthereform.
 4. The transformer assembly of claim 3, wherein the firstextending portion is positioned at a center of the planar base member.5. The transformer assembly of claim 4, wherein the planar base memberincludes a second extending portion and a third extending portionpositioned on opposite sides of the planar base member.
 6. Thetransformer assembly of claim 5, wherein the first PCB defines a secondopening and a third opening positioned on opposite sides of the firstPCB to receive the second extending portion and the third extendingportion of the planar base member, respectively.
 7. The transformerassembly of claim 6, wherein the magnetic core includes a first portionfor being positioned directly above the primary winding.
 8. Thetransformer assembly of claim 1, wherein the wire assembly is a Litzwire.
 9. The transformer assembly of claim 1, wherein the wire assemblydefines an opening to receive a first extending portion of the magneticcore.
 10. The transformer assembly of claim 1, wherein secondary windingis implemented as a metallic foil that is embedded within a plurality oflayers that form the first PCB.
 11. The transformer assembly of claim10, wherein the metallic foil is partitioned into a plurality of currentcarrying sectors, wherein the PCB defines a plurality of segmentspositioned on each layer of the plurality of layers., and wherein eachof the plurality of segments are disposed on the same positions for eachlayer.
 12. The transformer assembly of claim 11, wherein a first currentcarrying sector is positioned on a different segment for each layer toreduce parasitic currents in the assembly.
 13. The transformer assemblyof claim 1, further comprising a second PCB positioned above the firstPCB and the primary winding.
 14. The transformer assembly of claim 13,wherein the magnetic core surrounds at least a portion of the first PCBand the second PCB.
 15. The transformer assembly of claim 1 isimplemented in a direct current (DC) to DC converter.
 16. A powerconversion device comprising: a transformer assembly to receive an inputsignal, the transformer assembly including: a first printed circuitboard (PCB); a magnetic core positioned about the first PCB; a primarywinding implemented as a wire assembly and being positioned on a firstside of the PCB to interface with the magnetic core; and a secondarywinding embedded within the first PCB to interface with the primarywinding and the magnetic core to convert the input signal into aconverted output signal.
 17. The power conversion device of claim 16,wherein the wire assembly is a Litz wire.
 18. The transformer assemblyof claim 16, wherein the wire assembly defines an opening to receive afirst extending portion of the magnetic core.
 19. The transformerassembly of claim 16, wherein secondary winding is implemented as ametallic foil that is embedded within a plurality of layers that formthe first PCB.
 20. A transformer assembly comprising: a printed circuitboard (PCB); a magnetic core positioned about the PCB; a primary windingimplemented as a Litz wire and being positioned on a first side of thePCB to interface with the magnetic core; and a secondary windingembedded within the first PCB to interface with the primary winding andthe magnetic core to convert an input signal into a converted outputsignal.